Silicon carbide (SiC) is a hard chemical compound consisting of silicon and carbon. It occurs naturally as the mineral moissanite, but is typically manufactured on a large scale for use mainly as an abrasive and in ceramics.
It is made by heating a mixture of silica (sand) and finely ground carbon at high temperatures, between 1600 and 2500 degC in an electric furnace, with some salt and saw dust. This produces a finely powdered or granular product that has been used as an abrasive for more than a century.
In manufacturing, it is used as a support and shelf material in high-temperature furnaces for firing ceramics and glass. It also has a variety of uses, such as in brake linings, heating elements and thermistors.
It is a good conductor of heat, with excellent thermal shock resistance and dimensional stability. It is also very resistant to high pressures and temperature changes.
SiC can sublimate from a solid into a gas at temperatures up to 2700 degC, which is almost half the surface temperature of the sun. This makes it ideal for bearings, furnace parts and other applications in which the molten substance must be cooled rapidly.
It can be manufactured by two methods: reaction bonded or sintered. The latter method is preferred for electric heating element materials. Both methods can produce an impermeable unit. Regardless of bonding method, the impermeable units tend to be more resistant than the permeable ones to attacks by chemical substances.